The digestive system is critical for the well-being of individuals and of populations. The central objective of this training grant is to prepare young scientists for investigative and academic careers relevant to the digestive health of children. This grant will provide rigorous investigative training by immersing promising young scientists in opportunities at Washington University School of Medicine that address digestive health challenges of children worldwide. The rationale for this program is based on two premises: high quality research experiences soon after graduate or clinical training are critical for successful academic careers, and there is a shortage of trained individuals to solve problems relevant to, or caused by, the childhood digestive system. The program encompasses diverse disciplines and topics, but all mentors and projects are linked by three common motifs: 1. they perform research that directly relates to relevant questions, 2. individual mentored environments are robust, and 3. trainees are integrated into existing projects, and receive rigorous individual preparation for research careers. In this application, we expand our successful program that has previously focused on pediatric gastroenterology trainees to a very well qualified surgical trainee cohort. The program uses a three track system. Trainees in Track I (Microbial - Host interactions in the Gastrointestinal Tract), choose a project exploring the role of microbes in childhood intestinal health and well- being. In this Track, trainees can focus on specific pathogens or their mechanisms, or on polymicrobial microbiology (i.e., the microbiome). Track II (Cellular and Molecular Biology of the Developing Gastrointestinal Tract) trainees focus on the molecular and genetic aspects of congenital and acquired disorders of the childhood gastrointestinal tract. Track III (Translational Biology of the Gastrointestinal Tract) trainees us human subjects or human subjects' materials to delineate causes, treatments, and prevention of digestive disorders of childhood. This two year training program will be for individuals with M.D. and/or Ph.D. degrees in biomedical sciences. We will draw from our traditional base of pediatric gastroenterology fellows and qualified postdoctoral associates, and also enrich our applicant flow by opening training opportunities to surgical residents. This amalgamation of trainee pipeline and training opportunities under the support of this training grant will take full advantae of our growing and multi-level collaborations between pediatric gastroenterology and pediatric surgical research in our institution. The goal is to produce scientists with enduring interests in childhood gastrointestinal disorders, and the causes, treatments, and prevention of these illnesses.